1. Technical Field
The present invention relates to a semiconductor integrated circuit. More particularly, the present invention relates to a voltage control apparatus using a burn-in test where a stress test is applied to weak cells and peripheral logics so as to detect defective elements in advance, and a method of controlling a voltage using the same.
2. Related Art
In general, semiconductor integrated circuits, for example, dynamic random access memories (DRAMs) are subjected to a burn-in test process that applies a stress to the DRAMs at a voltage higher than an operation voltage and a high temperature so as to detect defective elements in advance before a packaging process. If the burn-in test process is performed, it is possible to detect defective cells and logic circuits.
Further, during the burn-in test process, an excessive stress is applied to a dielectric film of storage capacitors of cells where a data signal is stored at a high potential so as to screen out defective cells therefrom. The stress is applied to a gate oxide film of cell transistors so as to determine whether electric breakdown occurs in the gate oxide film.
In order to perform the burn-in operation, a DRAM needs to have an active-write-precharge operation pattern. The operation of the DRAM is divided into a row-fast (X-Fast) operation and a column-fast (Y-Fast) operation according to row address (X-Address) and column address (Y-Address) scan methods.
FIG. 1 is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a row-fast (X-Fast) operation, and FIG. 2 is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a column-fast (Y-Fast) operation.
In FIGS. 1 and 2, A0 to A(N) indicate active commands, W0 to W(N) indicate write commands, and P0 to P(N) indicate precharge commands.
When comparing structures shown in FIGS. 1 and 2, the number of times of active-precharge during a row-fast (X-Fast) operation is n times larger than that during a column-fast (Y-Fast) operation. This means that an amount of peak current is large during an active operation or a precharge operation.
That is, in the case of the column-fast (Y-Fast) operation, according to an active-precharge method, after a row address is activated, a write operation is performed such that the number of times of the write operation is as many times as the number of columns, and a precharge operation is performed. For this reason, a peak current according to the operation of a word line WL during the column-fast (Y-Fast) operation becomes 1/N times smaller than that during the row-fast (X-Fast) operation.
FIG. 3 is a timing diagram illustrating an active-precharge method when a voltage control apparatus according to the related art performs a row-fast (X-Fast) operation.
As shown in FIG. 3, in the general voltage control apparatus, if an active command ACT is input, an active signal ACTIVE is generated, and a potential of the word line WL is increased to a level of a bootstrapping voltage VPP according to the active signal ACTIVE. Since the word line WL that is discharged to a ground voltage VSS needs to be charged to the level of the bootstrapping voltage VPP, a large amount of current is instantaneously consumed.
In FIG. 3, reference character A indicates an instantaneous peak current that is generated according to the operation of a word line WL during an active operation, and reference character B indicates a peak current that is generated during a precharge operation. Reference character C indicates a peak current that is generated according to the operation of a sense amplifier.
However, as the capacity of a DRAM increases, the amount of operation current that flows through the DRAM increases. In particular, in the case of the burn-in test where an active-precharge operation is repeated for 48 to 72 hours with an external voltage VDD higher than an operation voltage, a large amount of peak current is generated during a row-fast (X-Fast) operation. The large amount of peak current causes a solder ball functioning as an external signal terminal to be melted during a packaging process of a semiconductor memory apparatus, which lowers a package yield and damages a burn-in socket.
According to another method in the related art, an amount of peak current is reduced by using an active-precharge method during a column-fast (Y-Fast) operation. However, when the burn-in test is performed through the column-fast (Y-Fast) operation, a peri-transistor formed in a peripheral region may be deteriorated, and it is difficult to accurately screen out defects of the peri-transistor.